I've got a fresh install of ArcGIS 10.0, and whenever I try and open a tool from the toolbox (for example, Project Raster) it takes literally 5 minutes to open the dialog, and then at least 30 seconds for any clicks I make in the dialog (for example, to select input files) to register.

Does anyone have any idea why this is? The rest of ArcGIS isn't too slow (at least, no more than normal) but using toolbox tools is just impossible! This doesn't happen on my laptop, and this computer is significantly faster than my laptop (this has 12Gb RAM, quad-core processor etc).

FYI, ArcGIS 10 still isn't multithreaded so it can't take advantage of your quad-core processor except for a few UI-related things. If you open Task Manager while you're running a hefty geoprocessing task you'll see the ArcGIS process is only using 25% of your CPU (1 of the 4 cores). Updating your Arc installation is a good first step but I'd start with SP2 and its associated patches, SP3 just came out a week or two ago and ESRI's track record of releasing bug-free updates isn't that great.
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Dan CNov 8 '11 at 18:52